1. Field of the Invention
The invention relates to a piezoelectric sensor having a layer of a piezoelectric material being applied to a supporting substrate.
The invention also relates to a method for manufacturing of such a piezoelectric sensor.
The invention also relates to a medical implantable lead comprising such a piezoelectric sensor.
2. Description of the Prior Art
Piezoelectric sensors of the above type are commonly used to detect and measure physical characteristics, such as fluid pressure, stress in mechanical structures and the like. Briefly, piezoelectric sensors transform deformations into electrical signals or pulses. Accordingly, they have a wide applicability and are frequently used in industrial and electronic applications.
A piezoelectric sensor of the above kind, may also be used in many different applications for monitoring various functions and organs inside a human or animal body. As such it may be used to monitor e.g. pressures inside tissue or body fluids. Hence, it can be used in for example a medical implantable lead connected to a pace maker to monitor blood pressure and/or heart rate inside a heart.
U.S. Pat. No. 6,571,130 discloses a medical implantable lead comprising a piezoelectric sensor, which in one embodiment is formed in a distal and surface of the lead and in another embodiment is formed as a ring or envelope surface of the lead.
Also, WO 02/34130 disclosed piezoelectric sensors for medical implantable leads, which are formed as tubes having the piezoelectric material applied on the outside of the supporting substrate or, on one embodiment, having the piezoelectric material formed as a self-supporting structure. On the outside, only a thin electrode layer is covering the outer surface of the piezoelectric sensor.
However, in many cases it is disadvantageous to have the piezoelectric material in direct contact with tissue and/or body fluids, e.g. blood, since then the piezoelectric material should preferably be made of a biocompatible and non-toxic material, which might exclude the use of certain materials that could have better characteristics in certain aspects, either electrically and/or mechanically.
Also the contacting of cables or coils to the electrodes can be problematic when in contact with body tissue or fluids since the connections, which normally are soldered or welded, will be more exposed.